Background: Although image-guidance systems have gained widespread acceptance for neurosurgical procedures, their role for extracranial surgery of the head and neck is yet to be defined. Objective: To describe the authors' experience with image-guidance systems and to measure the effects of image-guided technology on the performance of minimally invasive otolaryngological procedures. Design: Prospective cohort study. Methods: Optical- and electromagnetic-based image-guidance systems were used during the performance of endoscopic surgery on patients with disease of the paranasal sinuses, orbit, skull base, and temporal bone (n = 79). Results were compared with those in control patients who underwent similar surgery without image guidance during the same period (n = 42). Results: Intraoperative anatomical localization was accurate to within 2 mm at the start of surgery in all cases. Accuracy degraded by 0.89 +/- 0.20 mm (mean +/- SE) during the operative procedure. The use of an image-guidance system increased operating room time by a mean of 17.4 minutes per case (image-guidance group, 137.3 +/- 6.0 minutes [mean +/- SE]; control group, 119.9 +/- 5.7 minutes; P = .006) and increased hospital charges by approximately $496 per case. Intraoperative blood loss (image-guidance group, 178.4 +/- 18.0 mt [mean +/- SE]; control group, 149.4 +/- 20.1 mL) and complication rates (image-guidance group, 2.7%; control group, 4.7%) did not differ significantly between groups. Conclusions: Image-guidance systems can provide the head and neck surgeon with accurate information regarding anatomical localization in cases with poor surgical landmarks caused by extensive disease or prior surgery; however, the use of such systems is associated with increased operative time and expense.